After putting seven past an Indonesia XI at the weekend, the Gunners were in prolific form once again, though it wasn’t until first-half injury time that Giroud claimed his third of the evening, extending his pre-season record to five goals in 70 minutes.
The France international drilled his first shot past the keeper from a gorgeous Tomas Rosicky pass, curled his second home in some style and then secured his hat-trick with a dinked finish from an Alex Oxlade-Chamberlain pass.
The England international opened the scoring in the second half within 60 seconds of the restart, sending a fine shot into the top corner, before teenage substitute Chuba Akpom scored twice in three minutes with two close-range finishes.
Defender Ignasi Miquel completed the rout on 75 minutes before the home crowd were treated to a response when Tran Manh Dung converted with a rather fortunate finish.
Arsenal fielded a strong side in Hanoi and, after an unimpressive start, found themselves in front when Giroud claimed his third of pre-season following a lovely piece of invention from Tomas Rosicky. The Czech playmaker scooped a ball over the top of the defence for his colleague, who produced a thumping finish across goal that the Vietnam keeper could only turn onto the inside of the post and in with a faint touch of his arm.
Lukas Podolski was in rather wasteful mood and on 28 minutes he saw a golden chance escape him. Teed up by lively compatriot Serge Gnabry, Podolski showed impressive close control to lose his man before spurning the chance to take a shot at a virtually unguarded net in favour of rolling the ball right to open space, where he was expecting Giroud to arrive.
Vietnam attacked enthusiastically enough but lacked quality in the final third. Le Cong Vinh drifted one shot wide from 20 yards while a number of other poorly executed attempts failed to trouble Wojciech Szczesny.
Podolski then hit the post with a low effort across goal before Gnabry’s follow-up was expertly saved – and it was left to Giroud to end the half strongly as he claimed his hat-trick, his second goal coming when he latched onto a poor clearance to curl a lovely effort into the top corner.
Minutes after Nguyen Anh Duc failed to tuck a dangerous cross away at the back post, Giroud struck again, dinking the ball over the keeper after racing onto a through-ball from Oxlade-Chamberlain to claim his fifth goal in 70 minutes in pre-season.
Arsenal, as is custom, made a slew of changes at the break – young talents such as Gedion Zelalem and Akpom being given game time alongside experienced performers like Theo Walcott, who inside a minute of the restart teed up Oxlade-Chamberlain for a lovely finish into the top corner.
Akpom, who scored against an Indonesia XI, then made another bright impression when netting twice in three minutes to make it 6-0. The 17-year-old striker, who appears to have enjoyed a growth spurt over the summer, first received a pass from Aaron Ramsey to tuck his shot away and then rolled the ball into an empty net following good work from Zelalem and Oxlade-Chamberlain.
The striker was denied a hat-trick when a dangerous curling effort was headed away by a defender, Per Mertesacker having a header saved from Walcott’s subsequent corner, but Ignasi Miquel did make it 7-0 when tucking the ball under an unconvincing keeper following neat work from Thomas Eisfeld on the left.
Tran Manh Dung pulled one on with a fortunate finish, scuffing a cross over the head of replacement keeper Damien Martinez, before Vietnam were reduced to 10 men late on when sub keeper Tran Buu Ngoc handled outside the box to prevent Jack Wilshere from scoring.
It was a rather pointless outing for Arsenal in truth, and took on a potentially damaging hue in injury time when Ramsey was forced off with a fitness problem.